Patent GB-475773-A (GB)
Title: Improvements in and relating to gas valves and controlling arrangements therefor
IPC: F23N1/00
Filed: 1937-04-19
Abstract: 475,773. Fluid - pressure servomotorcontrol systems. JUNKERS & CO., GES. April 19, 1937, No. 11115. Convention date, May 8, 1936. [Class 135] A servomotor-control system for a gas burner of the kind in which the main valve is adapted to be closed completely under the control of a safety cut-off valve on the occurrence of dangerous working conditions and is also adapted to be regulated under the control of a regulating valve to adjust the supply of gas to the burner in accordance with the heat requirements of the apparatus, has a limit valve associated with the regulating control valve so that under this control the main valve can only be moved to a partly closed position permitting a limited supply of gas to the burner. In the form shown in Fig. 1a, the main valve 12 is actuated by gas pressure acting on a diaphragm 13 under the control of an auxiliary valve 21 co-operating with an adjustable seat and actuated by a thermosensitive tube 19 and an auxiliary valve 38 actuated by a thermo-sensitive plate subject to the heat of the pilot flame 40 which issues from a hole in the plate. The limit valve comprises a loose ball 28 and is actuated by a spindle 33 secured to the diaphragm 13. To obtain an igniting gas supply to the pilot burner, a self-closing valve 43 is operated to establish a byepass connection 42, 16 with the main inlet 10. In the position shown, the pilot flame is alight and the safety cut-off valve 38 open while the thermo-sensitive tube 19 is cold and its associated elastically supported valve closed. As the temperature of the tube rises, the valve opens to admit pressure to the actuating chamber 15 of the main valve and move the main valve towards its closed position. As the valve approaches its seat the limit valve 28 closes, thus preventing any further supply of pressure fluid and so holding the main valve against further closing movement. The conduit 34 connecting the chamber 15 to the valve 38 has a restriction 41 and is connected with the pipe 42 through a restriction 44, so that when the valve 38 is closed pressure builds up in the chamber 15 to close the main valve. In a modification, the valves 21 and 28 are arranged in parallel and control the inlet of pressure fluid to the actuating chamber which is connected through a restricted passage with an enclosed chamber on the other side of the diaphragm. Exhaust from this chamber is controlled by the safety cut-off valve. In a variant of this form the safety cut-off is arranged in the conduit connecting the main inlet with the other two auxiliary valves and the enclosed chamber beneath the diaphragm is vented to atmosphere. In another form, the main valve is actuated by two diaphragms of differing area, the space between them being connected to the inlet through a restriction and the safety cut-off control valve and to a vent pipe through a chamber on the other side of the larger diaphragm, the limit valve and the regulating auxiliary valve. In the form shown in Fig. 2a, inlet pressure fluid is fed to the chamber 15 above the actuating diaphragm 13 through a restriction 45 and is exhausted either through the two thermally actuated valves in series or through the limit valve 50 and the safety cut-off auxiliary valve also in series. The limit valve has a restricted leak 55 and is adapted to be unseated as the main valve approaches its seat by a collar 54 engaging a bracket depending from the valve member. Further modifications are described in which the limit valve is actuated by a diaphragm subject to the pressure in the gas pipe between the main valve and burner. The thermallyoperated safety cut-off valve may be replaced or supplemented by any other " safety " control and the regulating auxiliary valve may be replaced or supplemented by other " regulating " control valves.